Driven turbochargers provide an alternative to both superchargers and turbochargers. Driven turbochargers may reduce turbo lag, by allowing the engine system to drive the compressor when there is an insufficient amount of exhaust gases to drive the turbine. This is accomplished through either a mechanical connection through a transmission from the crankshaft, or an electric motor connected to the engine electrical system, either of which in turn transfers power to or from the turbo shaft. Driven turbochargers can provide turbo-compounding when excess exhaust energy is present, which drives the turbine during high engine load conditions.